The present invention generally relates to a magnetic disc system and a control technique therefor and more particularly to a technique which can effectively and profitably be applied to a control of a format write operation performed upon writing of data on a storage (recording) medium.
In a magnetic disc system which may be employed, for example, as an external storage device or equipment of an electronic computer system or the like, it is known that data are stored or recorded on a plurality of circular tracks provided concentrically on a rotatable magnetic disc serving as the storage medium by means of a magnetic head adapted to be positioned above a desired one of the tracks.
In this conjunction, it is noted that when a file or the like is to be implemented in a magnetic disc, a so-called format write operation for writing such control information as storage location of data on the recording medium or disc and on the track, the length of the data and other information is required to be performed simultaneously with the recording of the data. Further, with a view to preventing erroneous data reading in the future from the track for which the format writing of the control information has been performed, erasing operation is commonly practiced in succession to the format write operation for erasing the old data which may remain in the region located outside of the range where the format write operation has validly been performed on each of the tracks. However, performing such an erasing operation on the remnant or remaining region of the track means that the time required for restrainingly holding the magnetic head to the track is correspondingly lengthened. This involves an increase in the overall time taken for the input/output of data to or from the magnetic disc system itself and thus presenting a cause for degradation in the performance of the whole computer system inclusive of the magnetic disc system.
Under the circumstances, there has been developed a technique for protecting the system performance against degradation due to the erasing operation carried out in succession to the format write operation in the magnetic disc system, as disclosed, for example in U.S. Pat. No. 3,801,969 corresponding to Japanese Patent Publication JP-B-56-17692. According to this known technique, arrangement is made such that the erasing operation is performed internally within the magnetic disc system itself after the format write operation without resorting to the aid of a magnetic disc controller employed for controlling the magnetic disc system, to thereby spare the time for which the magnetic disc controller is occupied by the magnetic disc system.
Further, according to the technique disclosed in JP-A-61-241824, it is attempted to reduce the time taken for the format write operation by avoiding a duplicate erasing operation for a region for which the erasing operation has once been performed.
In either of the prior art techniques mentioned above, the erasing operation is still necessarily required more or less in succession to the format write operation. Thus, the magnetic disc system is placed in the occupied state at least until the erasing operation has been completed and is rendered to be incapable of reading other recorded data or executing a move or a like command of the magnetic head during the erasing period. In other words, the prior art magnetic disc system still suffers from the problem that a lot of time is taken for the data input/output operation as a whole, being accompanied by degradation in the utilization efficiency of the magnetic disc system as well as the data stored therein.